Electric discharge machines are operative to supply electric current pulses to a machining gap and to perform melt-removal and machining of workpieces by using discharge energy.
The conventional circuit configuration of a power supply apparatus therefor is disclosed in, for example, JP-UM-A-56-9890.
The power supply apparatus disclosed in this JP-UM-A-56-9890 has two modes of operations, which are a rough machining operation and a finish machining operation, as operations of this circuit. Between a circuit suited to the finish machining operation and a circuit suited to the rough machining operation is performed by changing over a switch. Switching elements respectively used in a charging circuit and a discharging circuit in the finish machining operation are utilized in a parallel circuit in the rough machining operation, and are thus effectively used. Consequently, the configuration of the power supply apparatus is compact and inexpensive.
Patent Document 1: JP-UM-A-56-9890 (pages 1 to 10, and FIG. 1)